Signal transmission circuit



SIGNAL TRANSMISSION CIRCUIT Filed Jan. 26, 1955 INCQMl/VG M00 ULA TED CARR/ER 7'0 SELECTOR OR OTHER PULSE RECEIVING EQUIPMENT //Vl/E/\/TOR RE". R5551; ER

Wm 6, 7/424 M ATTORNEY Patented Apr. 21, 1936 UNITED STATES PATENT OFFICE Application January 26, 1935, Serial Nb. 3,574

10 Claims.

This invention relates to signal transmission circuits, and more particularly, to pulse-receiving circuits.

Heretofore, in modulated carrier wave pulsereceiving circuits, it has been the practice to impress the rectified modulated carrier wave, for instance,through a filter, directly upon a relay or relays controlling the circuit to be operated in accordance with the received pulses. It has been found, however, that with variation in the transmission level of the incoming wave, considerable distortion resulted because, filters having relatively narrow band limits, the envelope of the resultant wave impressed on the relay or relays was substantially a sine wave rather than a series of pulses having an abrupt initiation and an abrupt cessation.

An object of this invention, therefore, is to improve modulated carrier wave pulse-receiving circuits, and, more particularly, to prevent or avoid distortion therein, resulting, for example, from carrier level variation.

A feature of the invention comprises the use of a gas-filled tube as a relay control means in a pulse-receiving circuit.

Another feature comprises the use of a plurality of gas-filled tubes as relay control means in a pulse-receiving circuit, one of the tubes causing the energization or operation of one or more relays, and another their deenergization or release.

Still another feature comprises the use of cold cathode tubes as relay control means in a pulsereceiving circuit.

A further feature comprises a pulse-receiving circuit comprising an incoming line, a rectifier, transformer, a pair of cold cathode gas-filled tubes, and a plurality of relays for operating upon a pulse-controlled circuit associated with the pulse-receiving circuit.

In accordance with this invention, the incoming modulated carrier wave is rectified, and the modulation frequency with harmonics is transmitted to the cathodes of a pair of gas-filled cold cathode tubes through a suitable transformer. One tube is caused to ionize and to cause the operation of a relay that holds itself operated and causes the operation of additional relays, one of which transfers potential from the anode of the tube to the anode of the second, and the other of which opens the circuit to a pulse-controlled circuit or apparatus. The reverse half of the wave causes ionization of the second tube and the release of the various relays to place the pulse-receiving circuit and pulse-controlled circuit or apparatus in condition for the reception of the next pulsing wave.

A more complete understanding of the invention will be obtained from the detailed description which follows, taken in conjunction with the single figure of the accompanying drawing, which shows a signal transmission circuit in accordance with this invention.

In accordance with the invention, the accompanying drawing, in general, shows an impulsereceiving circuit employing a pair of cold cathode, neon-filled tubes, intended primarily for use in a transmission system in which a carrier wave is interrupted, i. e., modulated, at dialing speeds, at the sending end of the system and is transmitted through band pass filters on other networks such that the envelope of the modulated carrier incoming to this receiving circuit is approximately sine wave in form, and in which the level of incoming carrier may vary considerably.

The function of the impulse-receiving circuit is to reproduce by relay contacts, the pulses of the dial at the sending end, such that negligible pulse distortion occurs, in spite of narrow band transmission and variation in carrier level. distortion is meant the amount by which the per cent make or break of the contacts of the pulse-reproducing relays in the receiving circuit differs from the per cent make and break of the dial contacts at the sending end.

Referring to the drawing, the modulated carrier is received over the incoming line wires Ill, II and is rectified by a Wheatstone bridge type, full-wave rectifier I2, preferably employing rectifier units l3 of the dry type, for instance, coppercuprous oxide units, connected across the line. The output terminals l4, iii of the rectifier are connected through conductors I6, I! with the terminals of the primary winding [8 of a transformer [9. The current passed by the rectifier comprises a direct current component and an alternating current component corresponding to the envelope of the modulated carrier. A condenser 28 is bridged across winding I8 to absorb the carrier ripples in the rectifier output current.

The transformer secondary comprises two windings 2|, 22 serially connected, the common terminal 23 being connected through conductor 24 with biasing battery 25 and one cathode 26 of each of the two gas-filled tubes 21, 54, which may be of the cold cathode, neon-filled type, and o to ground. The other terminals 28, 29 of the transformer secondary are connected through conductors 30, 3! and resistances 32, 33 with another cathode 34 of each of the tubes.

By pulse The anode 35 of tube 21 is normally connected through the winding 36 of a three-winding polar relay 31, the contact 38 and armature 39 of a second relay 40, and a resistance 4|, with battery 42. The anode of tube 54 is normally connected through a second winding 43 of the relay 31 wound in opposition to winding 36, to the contact 44 of relay 40. The third winding 45 of relay 31 is serially connected with the winding of relay 4|], and the winding of a. third relay 46, the battery 42 and a resistance 41, the circuit being normally open at the armature 48 and contact 49 of relay 31. Normally, armature 50 of relay 46 engages with contact 5| to close the circuit of line 52 leading to a selector or other pulsereceiving equipment to be controlled in accordance with the signal pulses received by the pulsereceiving circuit.

Voltages induced in transformer windings 2|, 22 are dependent upon the rate and amount of variation of current in the primary l8. For example, when primary current flows from conductor IE to conductor l1 and is increasing in magnitude, voltages are induced in the secondary windings in directions 29-23 and 2328. Voltage of winding 2| is added to that of the biasing battery 25, while that of winding 22 is subtracted, the potential between the cathodes in tube 21 is increased and that between the cathodes in tube 54 decreased, as long as the voltage of winding 22 is less than that of battery 25. When the primary current is decreasing, the secondary winding voltages are reversed and the cathode-tocathode potential of tube 21 is decreased and that in the other tube is increased, as long as the voltage in the winding 2| is less than that of battery 25.

In the first case, i. e., when the primary current is increasing, when the sum of winding 2| voltage and battery voltage exceeds the cathode breakdown potential, tube 21 ionizes between cathodes, while in the second case, when the sum of the winding 22 voltage and battery voltage exceeds the cathode breakdown potential of tube 54, the latter ionizes between cathodes. In either case, when the secondary winding voltage drops to zero, ionization of the gas path ceases since the maximum potential of battery 25 is maintained at less than the required sustaining potential. Battery 25, therefore, acts to increase the sensitivity of the circuit, and to prevent both tubes from ionizing on the same half cycle, this type of tube having a non-polar breakdown characteristic.

The voltage of battery 42 must be less than the anode-cathode breakdown potential of the tube but greater than the necessary sustaining voltage. For the relay armature positions shown, when an increase in primary current induces sufficient voltage in the secondary to produce breakdown between the cathodes of tube 21, anode-tocathode ionization occurs, causing a flow of current in winding 36 of relay 31. In operating, relay 31 looks itself through its Winding 45, an operating circuit for relays 40 and 46 being closed. The operation of relay 4|] transfers battery 42 from the anode of tube 21 to that of tube 54.

When the rate of decrease of primary current is sufficient to cause breakdown of tube 54, anode current in winding 43 of relay 3'! produces sufficient ampere-turns to overcome that of winding 46, and the effective ampere-turns of a biasing spring if one is associated with the relay 31. The latter releases, thereby releasing relays 40 and 46, battery 42 is transferred back to the anode of tube 21 and the circuit is restored to its original condition, armature 50 and contact 5| which had been separated on energization of relay 46 again making contact, resulting in a transfer to the controlled circuit of the received pulse.

Since tube 21 ionizes during the portion of the cycle in which the primary current is increasing in value, and tube 54 ionizes when the primary current is decreasing, it is evident that, if the same wave form of the current be maintained, the interval between ionization of the tubes for a given pulsing frequency, will remain essentially constant, even though the carrier level may vary considerably; provided the maximum rate of carrier level fluctuation is less than the minimum rate of change necessary to cause ionization of the tubes. Since the length of make and break periods of relay 3! and, consequently, of relay 46 are controlled by the ionization intervals, it follows that, for a given speed, the make and break periods of relay 46 are independent of carrier level. The maximum level, assuming per cent modulation in every case, is limited, for a given pulsing frequency, to the value which causes either secondary winding voltage plus the voltage of the source of anode potential to exceed the anode-cathode breakdown potential of either tube, or which causes the blasting volt- 1 age less the voltage of either secondary winding to have an absolute value greater than the cathode-to-cathode breakdown potential. Which of the two limiting conditions will determine the maximum level, depends upon the value chosen for the biasing voltage. In either case, the effect of exceeding this level will be that, at the beginning of a cycle of primary current, one tube will ionize as intended, but relay 40 may transfer battery to tube 54 quickly enough to allow it to break down during the same half cycle.

Resistances 32 and 33 are inserted to reduce the current drain on battery 25, and resistances 4| and 41 to reduce the current drain on battery 42 during the ionization and to regulate the relative biasing effects of windings 43 and 45 of relay 31; resistances 4| and 41 may be either external or included in the windings of relays 40 and 46. To be sensitive to low modulating frequencies, transformer l9 should have a reasonably high inductance. While any full wave rectifier might be used for rectifying the incoming modulated carrier, one employing coppercuprous oxide units is preferred as the most suit able for working into the low transformer primary impedance. Furthermore, while tubes 21 and 54 have been described as cold cathode neon tubes, cold cathode argon tubes or hot cathode gas-filled tubes would function as satisfactorily after readjusting circuit battery potentials to the proper value. The cold cathode neon tubes have the advantage, however, that there is no filament or cathode-heater power loss.

While this invention has been disclosed with reference to a single embodiment, it is to be understood that it is not limited thereto, but is to be considered as comprehending that which is included in the terms and spirit of the appended claims.

What is claimed is:

1. A transmission circuit comprising an incoming line for signal impulses, a plurality of cold cathode gas-filled tubes, means including a rectifier and a transformer for impressing signal impulses first on the cathode of one tube and subsequently on the cathode of another tube, each tube having a cathode connected to one output terminal of said transformer, a controlled circuit, and a plurality of relays associated with said tubes for controlling said controlled circuit in accordance with the rectified signal impulses and upon the ionization of said tubes thereby.

2. A transmission circuit comprising an input line, a pair of cold cathode tubes, means comprising a rectifier connected in said line and a transformer connected to the output of said rec tifier for impressing signal impulses on said tubes to cause first one and subsequently the other to ionize, each tube having a cathode connected in the output circuit of said transformer, a controlled circuit, and means associated with said tubes to be operated upon the ionization of said tubes in accordance with pulses received over said input line, to interrupt and to close said controlled circuit.

3. A transmission circuit comprising an incoming line for a modulated carrier wave, a rectifier having its input terminals connected to said line, a transformer connected to the output terminals of said rectifier, a pair of gas-filled tubes of the cold cathode type, each being caused to ionize by a different half of the rectified wave and each having its cathode connected to an output terminal of said transformer, a controlled circuit, and a plurality of relays associated with said tubes for controlling said controlled circuit in accordance with the rectified modulated carrier Wave.

4. A transmission circuit comprising an incoming line for a modulated carrier wave, a full wave copper-oxide rectifier having its input terminals connected to said line, a transformer connected to the output terminals of said rectifier, a pair of gas-filled tubes, each tube ionizing in response to a difierent half of the rectified wave and each having its cathode connected to an output terminal of said transformer, a controlled circuit, and a plurality of relays associated with said tubes for controlling said controlled circuit in accordance with the rectified modulated carrier wave.

5. In a pulse-receiving circuit, a pair of gasfilled tubes, each having a cold cathode, means for impressing a signal wave first on one cathode and subsequently on the second to cause the tubes to ionize, a plurality of relays, one of which has a plurality of windings, one winding being connected with the anode of one tube, a source of potential to be applied to said anode being normally in circuit with said winding, a second winding being connected with the anode of the second tube and being Wound in opposition to the other windings on said relay, a third winding being connected in series with the windings of the other relays, one of said other relays upon the ionization of the first tube and the energization of the multi-winding relay being, adapted to transfer the source of potential from the anode of the first tube to that of the second, and another of said other relays being adapted to interrupt and to close a pulse-controlled circuit in accordance with the signal impressed on the tubes, all relays deenergizing upon the ionization of the second tube.

6. A transmission circuit comprising an incoming line for a modulated carrier wave, a full- Wave copper-oxide rectifier having its input terminals connected to said line, a transformer connected to the output terminals of said rectifier,

' a pair of gas-filled tubes each having its cathode connected to an output terminal of said transformer, a controlled circuit, and a plurality of relays associated with said tubes for controlling said controlled circuit in accordance with the rectified modulated carrier wave, one of Said relays controlling the circuits for the other relays and having windings one of which is con.- nected to the anode of ,one tube and the other to the anode of the other tube, one winding being normally in series with a source of anode potential, and the other adapted to be connected to the same source of potential upon the ionization of the first tube, another of said relays transferring the source of anode potential from the anode of one tube to the other, and a third relay opening the controlled circuit upon the energization of the first relay, all of said relays being deenergized upon the ionization of the second tube.

7. A transmission circuit comprising an incoming line for a modulated carrier wave, a copperoxide rectifier having its input terminals connected to said line, a transformer connected to the output terminals of said rectifier, said transformer comprising a primary winding and a secondary having two windings with a common terminal, a condenser shunted across said primary winding, a pair of gas-filled tubes each having two cathodes and an anode, a source of potential connected between said common terminal and one cathode of each tube, the other terminals or said secondary windings being connected with the other cathodes of said tubes, a controlled circuit, and a plurality of relays and a source of potential associated with the anodes of said tubes for controlling said controlled circuit in accordance with the rectified modulated carrier wave.

8. A transmission circuit comprising an incoming line for signal impulses, a rectifier connected in said line, a transformer connected in the output circuit of said rectifier and comprising a primary and a secondary, said secondary comprising two windings having a common terminal, a pair of cold cathode neon tubes having two cathodes and an anode, a source of potential connected between said common terminal and One cathode of each tube, the other terminals of the secondary windings being connected to the other cathodes, a controlled circuit, and means associated with anodes of said tubes to be operated upon the ionization of said tubes in accordance with pulses received over said input line to interrupt and close said controlled circuit.

9. A transmission circuit comprising an incoming line for signal impulses, a copper-oxide rectifier connected in said line, a transformer connected in the output circuit of said rectifier and comprising a primary and a secondary, means shunted across said primary to absorb the carrier ripples in the rectifier output current, said secondary comprising two windings having a common terminal, a pair of cold cathode neon tubes having two cathodes and an anode, a source of potential connected between said common terminal and one cathode of each tube, the other terminals of the secondary windings being connected to the other cathodes, a controlled circuit, and means associated with anodes of said tubes to be operated upon the ionization of said tubes in accordance with pulses received over said input line to interrupt and close said controlled circuit.

10. A transmission circuit comprising an incoming line for signal impulses, a rectifier connected in said line, a transformer connected in other cathodes, a controlled circuit, and relay means associated with the anodes of said tubes to be operated upon the ionization of said tubes in accordance with pulses received over said input line to interrupt and close said controlled 5 circuit.

RALPH E. RESSLER. 

